1987 Evinrude 70hp

[gunny5]

Hey

my engine will not rev. I can run it up until 10-15 knots but if i rev more the engine sounds like its struggeling, like a slow moving car in high gear and nothing happens or decreases speed.
It starts on first turn and idle fine. What can be the problem?
I have changed fuel lines from External tank to engine and emptied the carbs.
My sparkpluggs are black and a little damp. Will do Comp test later today just in case.

// Mike

 

[jtexas]

Re: 1987 Evinrude 70hp

After the compression test, spark test: get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's a good indication that it's not firing in the heat & compression of the combustion chamber.

If you have good compression and spark, rebuild the carbs.

 

[gunny5]

Re: 1987 Evinrude 70hp

My compression is. 100, 110, 100
Is that ok?

The engine has no problem rev. in nuturael but under load. Can that be a carb issue?

 

[jtexas]

Re: 1987 Evinrude 70hp

classic symptom of dirty carbs. It can also be an ignition misfire so I suggest the spark test first because it's quick & easy. But chances are, you're going to be rebuilding your carbs. There's a carb rebuilding thread over in the "Engine FAQ" section of iboats. A service manual is a really good idea; I recommend the factory shop manual. Will pay for itself many times over.

compression is ok. conventional wisdom says no more than 10% difference between lowest & highest. might be worth taking a look at the "Decarb" thread over in the "Engine FAQ" section of iboats.

 

[gunny5]

Re: 1987 Evinrude 70hp

Problem solved!!!!
Cleaned all 3 carbs and now it work like a charm.
The problem was a clouged high speed ori in the top carb.
Thanks for all help!!

 

[patrick4266]

Re: 1987 Evinrude 70hp

Thanks Gunny for letting us know you fixed it and what the problem was.